Under a law passed in 1946 (now codified as 8 U.S.C. §1357), the CBP claims the right to search people and places without a warrant if the purpose of the search is to find illegal aliens and the search occurs within a “reasonable distance” of an international border. In regulations passed in 1953, that “reasonable distance” was defined as 100 miles from any land border or sea coast. Almost without comment, Congress made large swathes of the United States into a region where the Fourth Amendment is seriously weakened.

As the ACLU has noted, roughly two-thirds of Americans live within 100 miles of the oceans or the borders. And while the law in question specifically exempts dwellings from warrantless searches, that is the only exception. If you find yourself anywhere else in the warrantless zone, including cars, boats, trains, backyards, and (as we have seen) buses, and you are liable to be stopped and searched if CBP suspects you may be an illegal immigrant. It could be even worse than that; the law also allows the CBP to extend its Fourth Amendment–violating search power to areas greater than 100 miles with the permission of its commissioner.